Full disclosure: I’m trained as a traffic engineer, but I’m a disgruntled/disillusioned one (and a mod of !fuckcars), so that should give you some indication that my answers will be informed, but very much not unbiased.
Is there ever a traffic setting where this can be considered good?
The main thing to understand is that this design exists to mitigate the problems associated with a gigantic stroad, so strictly speaking, no, it’s never good because stroads are never good.
That sure makes it sound like a situation for an over/underpass with simple ramps for the major road / highway.
Your intuition is correct! By all rights, a road like this ought to be a freeway with grade-separated exits. But of course that’s expensive, so this is a “cheap” and worse alternative. (“Cheap” is in scare quotes because it’s still a wildly bad investment compared to just having sane non-sprawl-y urban planning to begin with, so you wouldn’t need so many ought-to-be-freeways everywhere and could afford to build fewer of them properly. This is the “solution” to a problem that shouldn’t exist.)
I know roundabouts in the US are considered socialist (or some other comparable reasoning)
American traffic engineers are coming 'round to roundabouts, actually!
That said, an intersection that’s a good case for a roundabout is pretty much the opposite of one that’s a “good” case for a Michigan left. Roundabouts are well-suited to situations where the major and minor streets have relatively similar traffic volumes and/or a lot of left turns, whereas a Michigan left is “appropriate” when you’ve got a low-traffic minor street crossing a very high traffic major highway, and left-turn volumes are low enough that you can treat them as an afterthought by exiling them to U-turns down the road.
Also, single-lane roundabouts work fine, but multilane roundabouts can get a bit iffy, especially at the extremely high traffic volumes and design speeds of the sort of road where a Michigan left would be considered. We’re talking about places where the major road might three lanes in each direction and have a 55-70 MPH (~100 km/h or more) speed limit, with those cars only having to stop occasionally when a car on the cross street trips the actuated signal. In a case like that, forcing all traffic to slow down significantly for a roundabout might not be seen as acceptable.
Full disclosure: I’m trained as a traffic engineer, but I’m a disgruntled/disillusioned one (and a mod of !fuckcars), so that should give you some indication that my answers will be informed, but very much not unbiased.
The main thing to understand is that this design exists to mitigate the problems associated with a gigantic stroad, so strictly speaking, no, it’s never good because stroads are never good.
Your intuition is correct! By all rights, a road like this ought to be a freeway with grade-separated exits. But of course that’s expensive, so this is a “cheap” and worse alternative. (“Cheap” is in scare quotes because it’s still a wildly bad investment compared to just having sane non-sprawl-y urban planning to begin with, so you wouldn’t need so many ought-to-be-freeways everywhere and could afford to build fewer of them properly. This is the “solution” to a problem that shouldn’t exist.)
American traffic engineers are coming 'round to roundabouts, actually!
That said, an intersection that’s a good case for a roundabout is pretty much the opposite of one that’s a “good” case for a Michigan left. Roundabouts are well-suited to situations where the major and minor streets have relatively similar traffic volumes and/or a lot of left turns, whereas a Michigan left is “appropriate” when you’ve got a low-traffic minor street crossing a very high traffic major highway, and left-turn volumes are low enough that you can treat them as an afterthought by exiling them to U-turns down the road.
Also, single-lane roundabouts work fine, but multilane roundabouts can get a bit iffy, especially at the extremely high traffic volumes and design speeds of the sort of road where a Michigan left would be considered. We’re talking about places where the major road might three lanes in each direction and have a 55-70 MPH (~100 km/h or more) speed limit, with those cars only having to stop occasionally when a car on the cross street trips the actuated signal. In a case like that, forcing all traffic to slow down significantly for a roundabout might not be seen as acceptable.